The present invention relates to a blowing agent, premix and process for preparing a rigid polyurethane foam or polyisocyanurate foam.
It is well established that a rigid polyurethane foam or polyisocyanurate foam is prepared by reacting a polyol and an isocyanate in the presence of a blowing agent, a reaction catalyst, a foam stabilizer and other additives. More specifically, the isocyanate is generally reacted with a premix of the polyol, the blowing agent, the reaction catalyst, the foam stabilizer and the additives in the industrial production of rigid polyurethane foam or polyisocyanurate foam.
At present, 1,1-dichloro-1-fluoroethane (HCFC-141b) is commonly used as the blowing agent for the preparation of rigid polyurethane foam or polyisocyanurate foam. HCFC-141b has the capability to destroy the ozone layer, even though the capability is low. It has been therefore decided to use HCFC-141b transiently and prohibit the use of HCFC-141b as the blowing agent after the end of the year 2003 in Japan.